We investigated both theoretically and experimentally open-ended coplanar waveguide resonators with rf SQUIDs embedded in the central conductor at different positions. These rf SQUIDs can be tuned by an external magnetic field and thus may exhibit the non-centrosymmetric nonlinearity of χ(2) type with suppressed Kerr nonlinearity. We demonstrated that this nonlinearity allows for efficient mixing of λ/2 and λ modes in the cavity and thus enables various parametric effects with three wave mixing. These effects are the second harmonic generation, the halftone generation, the parametric amplification in both degenerate and non-degenerate regimes and deamplification in degenerate regime.

中文翻译：

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具有非中心对称非线性的超导微波谐振器

我们从理论上和实验上研究了开放式共面波导谐振器，射频 SQUID 嵌入在不同位置的中心导体中。这些 rf SQUID 可以通过外部磁场进行调谐，因此可能表现出非中心对称非线性 χ(2个) 具有抑制克尔非线性的类型。我们证明了这种非线性允许有效混合 λ/2个 和λ腔中的模式，从而实现具有三波混频的各种参数效果。这些影响是二次谐波生成、半色调生成、退化和非退化状态下的参数放大以及退化状态下的去放大。